Apparatus for milling tubular strings in well bores



Sept. 8, 1964 D. E. LAMPHERE 3,147,536

APPARATUS FOR MILLING TUBULAR STRINGS IN WELL BORES Filed Oct. 27, 19612 Sheets-Sheei. l

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Sept. 8, 1964 D. E. LAMPHRE 3,147,535

APPARATUS FOR MILLING TUBULAR STRINGS IN WELL BORES Filed oct. 27, 19612 sheets-sheet 2 lNVEN TOR.

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United States Patent O David E. Lamphere, Fullerton, Calif., assignor,assignments, of three-fifths to Archer W. i and one-fifth to .lean K.Lamplrere, both of F llerton, Calif., and one-iifth to Archer W.Kammerer, Jr.,

Houston, Tex.

Filed Oct. 27, 1961, Ser. No. 148,172 Claims. (Cl. 29-1tl6) The presentinvention relates to subsurface well bore appar-atus, and moreparticularly to apparatus for milling away liners, casings, and similarconduit strings, while disposed in well bores.

Milling apparatus for cutting and milling away conduit strings in wellbores have been proposed, the apparatus including circumferentiallyspaced sets of longitudinally aligned blades or blade segments separatedfrom one another by a gap or slot, so that .a worn blade or segmentbreaks off near the end of its useful life and can be circulated out ofthe well bore. The laligned blade or segment there/above is then spacedabove the end of the conduit string by a distance at least equaling thelongitudinal extent of the gap or slot. It cannot come into play toperform its milling action on the conduit string until othercircumferentially spaced blades of the apparatus have been worn awaysufficiently to allow lowering of the apparatus along the conduitstring. As a result, only some of the circumferentially spaced bladesare sometimes effective for milling action on the conduit string,retarding the rate of milling land also tending to decrease the usefullife of the entire apparatus. It is also a fact that the aligned bladeor segment above the severed part initially therebelow is notimmediately eifective to mill away the conduit string upon engaging it,since it, at rst, tends to slide around the conduit string unitl a sharpleading blade edge is formed by the abrading action of the conduitstring on its lower end. The necessity for the sharp leading blade edgeto be formed also increases the time required to mill away the conduitstring.

Accordingly, an object of the ypresent invention is to provide millingapparatus for cutting away a conduit string disposed in a well bore,which is capable of performing its milling action in a more rapidmanner, and which possesses an increased effective life.

Another object of the invention is to provide milling apparatus forcutting away a conduit string disposed in a well bore and which includeslongitudinally aligned cutter blades or blade segments, there being asharp cutting edge or portion on an upper blade or segment immediatelyavailable for action upon the conduit string after a lower blade orsegment has worn away or broken off.

A further object of the invention is to provide milling apparatus forcutting away a conduit string in a well bore and which includeslongitudinally aligned blades or segments, there being hardfacingmaterial available for milling `action on the conduit string disposedacross the slots, grooves or gaps separating the blades or segments,thereby increasing the milling life of the tool and diminishing the timerequired to mill away a desired length of the conduit string.

This invention possesses many other advantages, and has other objectswhich may be made more clearly apparent from a consideration of severalforms in which it may be embodied. Such forms are shown in the drawingsvaccompanying and forming part of the present specification. These formswill now be described in detail for `the purpose of illustrating thegeneral principles of the invention; but it is to be understood thatsuch detailed description is n ot to be taken in a limiting sense, sinceICC the scope of the invention is best dened by the appended claims.

Referring to the drawings:

FIGURE l is a side elevational view, the parts broken away, or" amilling apparatus disposed in a well bore and operating lupon a conduitstrin-g located therewithim FIG. 2 is an enlarged longitudinal sectionof a portion of the yapparatus disclosed in FIG. l, after part of theapparatus has worn away ythrough use;

FIG. 3 is a cross-section taken along the line 3-3 on FIG. l;

FIG. 4 is a side elevational view of a modified form of millingapparatus;

FIG. 5 is a side elevational view of still another embodiment of theinvention;

FIG. 6 is a side elevational view of still another species of theinvention.

In the form of invention illustrated in FIGS. 1 to 3, inclusive, theapparatus A is a milling tool embodying a tubular body 10 having anupper threaded connection 1l, such as -a threaded box, for threadedattachment to the companion pin end 12 of a string of drill pipe Bextending to the -top of the wel-l bore C. The milling apparatus isparticularly designed for milling or cutting away a tubular string Ddisposed in the well bore, such as a string of casing, liner or tubing.The tubular body 10 has a central passage 13 therethrough for receivingdrilling fluid pumped down the drill pipe B, this duid dischargingthrough one or more ports or nozzles 14 in a lower pilot bit portion orguide 15 integral with the body 1t), carrying the cuttings from thedrilling region 11pwardly through the annulus E -around the drill pipeto the top of the well bore. The pilot or guide portion 15 preferablyhas an effective diameter slightly less than the inside diameter of theconduit string D to be disintegrated, in order to appropriately centerthe tool A therewithin.

The tubular conduit D, such as a liner or casing, is milled away by theaction of circumferentially spaced sets of cutter blades 16 integralwith or otherwise suitably secured to the body 10 of the tool andextending generally radially thereof. Each set 16 preferably includes aplurality of longitudinally aligned blade elements or segments 17, 18,adjacent segments being separated by a transverse gap, slot or groove19, which may be inclined in an upward and inward direction from theouter longitud-inal surface 20 of each blade toward the axis of thetubular body. In effect, each set 16 constitutes a single bladeseparated into segments 17 or 18 by the gaps, slots or grooves 19. Eachblade 16 merges into a rib or pilot portion 21 that will conform closelyto the inner wall of the tubular conduit D to be milled away, in orderto assist in centering the tool with respect to the tubular conduitstring. Above the centering portion 21 is the lowermost part 22 of eachblade, which also preferably tapers upwardly and inwardly, and which isadapted to engage the upwardly facing end F of the tubular conduit toperform a milling action thereon.

The leading face 23 of each set of blades is hardfaced by welding orbrazing suitable hardfacing material 24 thereto. The hardfacing materialmay, by way of example, be sintered tungsten carbide particles, tungstencarbide, titanium carbide, or the like, which are welded, brazed orotherwise deposited on the leading faces in a known manner, and whichextend from the lowerrnost ends 22 of the milling blade memberspreferably to their uppermost ends 25. The lowermost ends 22 of theblade 16 all lie in the sarne position, that is, circumferentiallyaligned, so as to be capable of simultaneously operating upon the upperend F of the tubular conduit D Fbe disintegrated.

In the operation of the apparatus A, it is lowered in the well bore onthe lower end of the string of drill pipe B until the pilot or guideporti'on 15, 21 enters the tubular Conduit D and the lower ends 22 ofthe blades 16 engages the upper end F of the tubular conduit. The drillpipe B and the apparatus A are then rotated at a proper speed, suitabledrilling weight `being imposed on the apparatus to force the lower ends22 of the blades against the upper end F of the tubular member. Thehardfacing material 24 on the leading faces 23 of the blades acts uponthe steel, or other material, of which the tubular string is made andreduces the same to cuttings, the cuttings being carried away bythedrilling mud or other drilling iluid pumped down the drilling stringB and through the central passage 13 of the apparatus body 10,discharging from the ports and nozzles 14. The mud and cuttings owupwardly through the arcuate spaces between the circumferentially spacedblades 16 and then around the drill pipe B to the top of the well boreC.

The blades 16 cut the tubular conduit D away in a downward direction. Asmilling away of the tubular conduit D proceeds, the latter itself cutslongitudinal grooves 30 in the blades 16. Since the cutter blades havethe hardfacing material 24 applied to them over substantially the entiresurface of their leading faces 23, there is always hardfacing materialon a blade available for action upon the upper end F of the tubularconduit. As the tubular conduit D cuts substantially through a bladesegment 17 or 18, the outer part 31 of such segment breaks off or away(FIG. 2). However, it is of insufficient size to interfere with thecontinued milling action of the apparatus on the tubular conduit D andwill be flushed by the drilling iluid in an upward direction around thedr-ill pipe B to the top of the well bore C. As each segment 17 or 18breaks away, the next segment or blade element thereabove engages theupper endF of the conduit string and will continue the milling actionupon the conduit string to cut it away in a downward direction.

In the form of invention illustrated in FIGS. 1 to 3, the gaps, slots orgrooves 19 in the longitudinally extending blade sets 16 are staggeredwith respect to one another,

so that when one blade segment, such as segment 18, is cut away by theaction of the conduit string, a blade segment of another set, such assegment 17, circumferentially spaced therefrom, is still effective foroperation upon the conduit string. The blades 16 of the apparatus,therefore, will not tend to flare the conduit string outwardly, whichwould interfere with continued disintegration of the latter by themilling apparatus A. Such a general arrangement is illustrated anddescribed in Patent No. 2,855,994, to Archer Vl. Kammerer, Jr., patentedOctober 14, 195 8, for Milling Apparatus. Although the milling apparatusillustrated inthe patent is very effective in milling away a conduitstring, such as a liner disposed in a well bore, the` longitudinal gapor space 19 between aligned blade segments 17 or 18 means that an uppersegment cannot begin its milling operation after a lower segment hasbeen worn away and removed until a sufcient length of the conduit stringhas been milled away by other blades and longitudinal grooves Si) worntherein as to bring the lowermost end of an upper segment into contactwith the conduit string. Moreover, it is found that the lower ends ofthe upper segments may not be sharp and immediately effective to performa milling action on the conduit string. The body of metal of a bladeV16, which is normally steel, must first be worn away by the upper end Fof the conduit string before the hardfacing material 24 is in a sharpstate, to begin its cutting action on the conduit string.

The aforenoted difficulty is overcome in the present case by extendingthe hardfacing material 24 applied to the leading face 23 of each blade16 across the slot or vgroove 19 between aligned blade segments. Thus,as a lower segment 17 or 1S breaks away, suflicient hardfacing material24a still adheres to an upper segment that was aligned therewith, anddepends below the body metal of `the upper segment as to, in elect,bridge the gap, groove or slot 19 and be promptly effective foraccomplishing a milling action upon the upper end F of the liner D, orother conduit string. Moreover, since the hardfacing material 24a isextending below the body metal of the blade, which is usually steel, itis in a sharp condition and promptly effective for disintegrating theconduit string D. As the conduit string wears the groove 30 upwardlythrough the depending hardfacing material 24a, it will eventually engagethe body metal of the segment thereabove and continue to wear such bodymetal away to a greater extent than the hardfacing material, since thebody metal is softer. The hardfacing material 24 always extends slightlybelow the body metal, presenting a sharp cutting surface for action uponthe upper end F of the conduit string.

rThe form of invention disclosed in FIG. 4 is substantially the same asshown in FIGS. 1 to 3, inclusive. However, the transverse slots orgrooves 19a do not extend completely through the body metal of eachblade 16, in order to separate it into aligned segments 17 or 18.Instead, each groove or slot 19a extends from the trailing face 40 ofeach blade 16 toward its leading face 23, but not completely across theentire thickness of the blade, leaving a weakened section or bridgingportion 41 between adjacent sections 17, 17 or 18, 18 to which thehardfacing material portion 24a is welded, brazed, or otherwise suitablyattached. The weakened section 41, which, for example, may be of theorder of an eighth of an inch in thickness, will have insufficientstrength to prevent a lower segment lfrom breaking off after it has beensubstantially completely cut through by the action of the liner D, orother conduit string. However, after it does break oif, there will behardfacing material 24a adhering to the weakened section 41, which canact upon the upper end F of the tubular'- conduit string and assist incutting it away as the result of rotation of the apparatus A by thestring of drill pipe B and the imposition of suicient drilling weightthereon. The weakened section 41 provides a backing for the hardfacingmaterial 24a and assures that such hardfacing material will depend belowthe main body of the blade segment or section above and adjacent to theone broken away, being available and effective for action upon theconduit string D. Thus, a portion 41 of the longitudinally extendingblade across its gap, slot or groove 19a is available for action uponthe conduit string, in order that all of the blades 16 are always actingupon the conduit string, even when the upper end of the latter isdisposed in the region of the slot or groove 19a of a blade. Moreover,the upper section of a blade is immediately in a sharp condition forprompt milling action on the upper end F of the conduit string disposedin the well bore C.

In the form of invention disclosed in FIG. 5, the slots or grooves 19ein each longitudinally aligned set of blades 16a all lie in the sametransverse position, or in circumferential alignment, rather than beingstaggered as disclosed in FIG. 1. The hardfacing material 24a on theleading faces 23 of each blade set still extends across the slots,grooves or gaps 19C. Upon the Wearing away or breaking offl of a lowersegment, such hardfacing material 24a will still extend below the lowerend ofthe next adjacent upper segment 17a and is capable of immediateaction upon the inner or other conduit string D.

The embodiment of invention shown in FIG. 6 is essentially the same asillustrated in FIG. 4, in that the slots 4or grooves 19d do not 'extendcompletely through each blade set 16 to separate it into alignedsegments 17a. Instead, each slot or groove 19d extends from the trailingface 40 substantially to its leading face 23 leaving a lrelatively thinweakened section 41 integrating the segments of the body. The hardfacingmaterial 24, however, is disposed on the leading faces of all of thesegments 17a and also on the leading face of the interconnectingweakened portions 41. In FIG. 6, the slots or grooves 19d in the sets ofblades are not staggered with respect to one another, as illustrated inFIG. 4, but lie in the same transverse positions. In all respects,however, the milling apparatus of FIG. 6 operates in the saine manner asthe milling apparatus illustrated in FIG. 4.

I claim:

1. In apparatus for milling away a tubular conduit disposed in a wellbore: a tubular body adapted to be secured to a drill string and havinga fluid passage therein; longitudinally aligned cutter blade segmentsseparated from each other by a slot of substantial axial extent andcarried by and extending generally radially outwardly of said body foroperation upon an upwardly facing end portion of the tubular conduit; abridging portion integral with said blade segments and extending acrosssaid slot at the leading faces of said segments; said bridging portionbeing substantially thinner than said blade segments to provide aweakened section between adjacent segments adapted to break anddisconnect the outer portion of a lower segment from the upper segmentafter said lower segment has ben substantially completely cut through bythe tubular conduit; and hardfacing material on the leading faces ofsaid segments and on the leading face of said bridging portion.

2. In apparatus for milling away a tubular conduit disposed in a wellbore: a tubular body adapted to be secured to a drill string and havinga fluid passage therein; sets of circumferentially spaced cutter bladescarried by and extending generally radially outwardly of said body foroperation upon an upwardly facing end portion of the tubular conduit;each set comprising longitudinally aligned blade segments separated fromone another by a slot of substantial axial extent; a bridging portionintegral with said segments in each set and extending across said slotof each set at the leading faces of said segments; each of said bridgingportions being substantially thinner than said blade segments to providea weakened section between adjacent segments adapted to break anddisconnect the outer portion of a lower segment from the upper segmentafter said lower segment has been substantially completely cut throughby the tubular conduit; and hardfacing material on the leading faces ofsaid segments and on the leading face of each of said bridging portions.

3. In apparatus for milling away a tubular conduit disposed in a wellbore: a tubular body adapted to be secured to a drill string and havinga iluid passage therein; sets of circumferentially spaced cutter bladescarried by and extending generally radially outwardly of said body foroperation upon an upwardly facing end portion of the tubular conduit;each set comprising longitudinally aligned blade segments separated fromone another by a slot of substantial longitudinal extent to provide awide gap therebetween; and hardfacing material on the leading faces ofsaid cutter blades and extending substantially across said slots; theslots separating the blade segments of one set being longitudinallyoffset with respect to the slots separating the blade segments of anadjacent set.

4. ln apparatus for milling away a tubular conduit disposed in a wellbore: a tubular body adapted to be secured to a drill string and havinga fluid passage therein; sets of circumferentially spaced cutter bladescarried by and extending generally radially outwardly of said body foroperation upon an upwardly facing end portion of the tubular conduit;each set comprising longitudinally aligned blade segments separated fromone another by a slot of substantial axial extent; a bridging portionintegral with said segments in each set and extending across said slotof each set at the leading faces of said segments; each of said bridgingportions being substantially thinner than said blade segments to providea weakened section between adjacent segments adapted to break anddisconnect the outer portion of a lower segment from the upper segmentafter said lower segment has been substantially completely cut throughby the tubular conduit; and hardfacing material on the leading faces ofsaid segments and on the leading face of each of said bridging portions,the slot separating the blade segments of one set being longitudinallyoifset with respect to the slot separating the blade segments of anadjacent set.

5. In apparatus for milling away a tubular conduit disposed in a wellbore: a tubular body adapted to be secured to a drill string and havinga fluid passage therein; sets of circumferentially spaced cutter bladescarried by and extending generally radially outwardly of said body foroperation upon an upwardly facing end portion of the tubular conduit;each set comprising longitudinally aligned blade segments separated fromone another by a slot of substantial axial extent; a bridging portionintegral with said segments in each set and extending across said slotof each set at the leading faces of said segments; each of said bridgingportions being substantially thinner than said blade segments to providea weakened section between adjacent segments adapated to break anddisconnect the outer portion of a lower segment from the upper segmentafter said lower segment has been substantially completely cut throughby the tubular conduit; and hardfacing material on the leading faces ofsaid segments and on the leading face of each of said birdging portions,the slot separating the blade segments of one set beingcircumferentially aligned with the slot separating the blade segments ofan adjacent set.

References Cited in the tile of this patent UNITED STATES PATENTS2,830,795 Center Apr. 15, 1958 2,846,193 Chadderon Aug. 5, 19582,855,994 Kammerer Oct. 14, 1958 2,999,541 Kinzbach Sept. 12, 1961

3. IN APPARATUS FOR MILLING AWAY A TUBULAR CONDUIT DISPOSED IN A WELLBORE: A TUBULAR BODY ADAPTED TO BE SECURED TO A DRILL STRING AND HAVINGA FLUID PASSAGE THEREIN; SETS OF CIRCUMFERENTIALLY SPACED CUTTER BLADESCARRIED BY AND EXTENDING GENERALLY RADIALLY OUTWARDLY OF SAID BODY FOROPERATION UPON AN UPWARDLY FACING END PORTION OF THE TUBULAR CONDUIT;EACH SET COMPRISING LONGITUDINALLY ALIGNED BLADE SEGMENTS SEPARATED FROMONE ANOTHER BY A SLOT OF SUBSTANTIAL LONGITUDINAL EXTENT TO PROVIDE AWIDE GAP THEREBETWEEN; AND HARDFACING MATERIAL ON THE LEADING FACES OFSAID CUTTER BLADES AND EXTENDING SUBSTANTIALLY ACROSS SAID SLOTS; THESLOTS SEPARATING THE BLADE SEGMENTS OF ONE SET BEING LONGITUDINALLYOFFSET WITH RESPECT TO THE SLOTS SEPARATING THE BLADE SEGMENTS OF ANADJACENT SET.